1. Field of the Invention
The invention relates to helmets for protecting the user's head during sporting activities. In particular, the invention relates to helmets to be used for skiing, snowboarding, biking, skateboarding, roller-skating, kayaking, and other sports.
Such helmets are required in sports such as mountain biking, competitive skiing, speed skating or the so-called “aggressive” roller-skating, for example. In addition, the use of such helmets is also strongly recommended for leisure biking and skiing.
2. Description of Background and Relevant Information
Various techniques have been used in the past to manufacture helmets of the aforementioned type. A particular one of these techniques is widely used in the manufacture of motorcycle and motorbike helmets and in the manufacture of certain ski helmets. Specifically, a rigid and relatively thin shell or cap is made by injection (PC, ABS) or by any other appropriate means (for example, by layering of various resin-impregnated layers of fabric). The shell is then fitted with comfort and/or shock-absorbing elements having an under cap of an expanded polystyrene (EPS), foams, fabrics. This technique enables helmets to be manufactured with a closely fitting contour.
Typically, such a helmet can cover the user's entire skull and also the ears, even the user's jaw. Through this technique, it is easy to mass produce single-piece shells with a maximal head coverage, at reasonable cost. Indeed, after the injection of the shell, even when the latter has full coverage, the shell remains deformable to enable removal from the mold. The disadvantage of this technique is that helmets made in this manner are rather heavy. Yet the weight of a helmet is a determining factor not only in competition but also in leisure activities where the heavier the user feels the helmet is, the less likely he/she is to wear it.
Another manufacturing technique is called “in-mold”. In this technique, most of the helmet is made in the same mold. Once the helmet is removed from the mold, it is equipped with a chin strap, and possibly with a comfort lining and other accessories. In practice, the outer skin of the shell, referred to as a “microshell”, is made independently. For example, this skin can be a polycarbonate sheet. This sheet is thermoformed so as to take the final shape of the outer surface of the helmet. This sheet is thin (generally, less than or equal to 1 millimeter). After trimming and cutting, the sheet is positioned in a mold with a polystyrene type material. The heat and the steam introduced in the mold trigger the expansion of the polystyrene until it fills up the volume of the mold and bonds with the polycarbonate sheet. Upon removal from the mold, the helmet is formed as a thick expanded polystyrene shell molded over an outer skin. Such a helmet has no flexibility and, therefore, unless expensive molds are used, this technique is only used to make light-weight helmets, the covering area of which does not include the zone covering the ears. For example, if one were to compare the covering area of a helmet to a sphere, it would be said that this technique prevents having a covering surface that cannot be contained in half a sphere. In practice, this technique is used for summer helmets having a shell that does not include parts for protecting the ears.
Another disadvantage of the so-called “in-mold” technology is that it is not possible to guarantee a precise positioning of the decorations on the helmet. The decoration is laid flat on the sheet that will be thermoformed, then placed in the mold with the polystyrene. During the thermoforming and the expansion phase of the polystyrene, it is very difficult to maintain the decoration lines intact, so that a line intended to be straight is blurred on the final helmet.
One technique used for decorating a helmet is to put a plurality of sheets in the mold, each of a different color. After the molding stage and the expansion of the polystyrene, the helmet has portions of its outer surface in different colors. This decoration technique also has its limits in terms of the quality of the finish because, in view of the imprecise positioning of the sheets in the mold, it is necessary to provide a substantial clearance (several millimeters) between the two sheets. On the finished product, the expanded polystyrene remains visible between the two colored sheets and the border between the two sheets is irregular.